The present invention relates in general to myocardial ischemia (or myocardial infarction) diagnosis and analysis, and, in particular, to an system and method for providing diagnosis and monitoring of myocardial ischemia for use in automated patient care throughout disease onset, progression, regression, and status quo.
Presently, myocardial ischemia, usually from the narrowing of the coronary arteries as a result of atherosclerosis, is one of the leading causes of cardiovascular disease-related deaths in the world. Clinically, myocardial ischemia involves a decreased oxygen and nutrient delivery to the myocardium resulting from diminished coronary artery blood flow which in turn leads primarily to abnormalities of left ventricular function and cardiac rhythm and the consequences thereof. Myocardial ischemia occurs when the demands of the heart for oxygen and nutrients are not met commensurately by available blood supply. The physiological effects of myocardial ischemia range from minimal to a complete failure of cardiac pumping function depending upon the degree of myocardial involvement and/or associated cardiac rhythm abnormalities. Clinical manifestations of myocardial ischemia include chest pain or discomfort (angina); respiratory distress, including shortness of breath; fatigue; reduced exercise capacity or tolerance; and nausea.
Several factors make the early diagnosis and prevention of myocardial ischemia, as well as the monitoring of the progression of myocardial ischemia, relatively difficult. First, the onset of myocardial ischemia is generally subtle and sometimes occurs without any clinical manifestations perceptible to the patient. Often, the symptoms are mild and ignored. The patient may also compensate by changing his or her daily activities in an unconscious manner to minimize symptoms. As a result, myocardial ischemia can remain undiagnosed until more serious problems arise, such as severe congestive heart failure leading to cardiac arrest or pulmonary edema. Moreover, the susceptibility to suffer from myocardial ischemia depends upon the patient""s age, sex, physical condition, and other factors, such as diabetes, blood pressure, cholesterol and homocystine levels. No one factor is dispositive. Finally, annual or even monthly checkups provide, at best, a xe2x80x9csnapshotxe2x80x9d of patient wellness and the incremental and subtle clinicophysiological changes which portend the onset or progression of myocardial ischemia often go unnoticed, even with regular health care. Documentation of subtle changes following initiation of therapy, that can guide and refine further evaluation and therapy, can be equally elusive.
Nevertheless, taking advantage of frequently and regularly measured physiological measures, such as recorded manually by a patient, via an external monitoring or therapeutic device, or via implantable device technologies, can provide a degree of detection and prevention heretofore unknown. For instance, patients already suffering from some form of treatable heart disease often receive an implantable pulse generator (IPG), cardiovascular monitor, therapeutic device, or similar external wearable device, with which rhythm and structural problems of the heart can be monitored and treated. These types of devices are useful for detecting physiological changes in patient conditions through the retrieval and analysis of telemetered signals stored in an on-board, volatile memory. Typically, these devices can store more than thirty minutes of per heartbeat data recorded on a per heartbeat, binned average basis, or on a derived basis from, for example, atrial or ventricular electrical activity, ST and T wave electrocardiographic changes, coronary sinus blood flow and composition, cardiac enzyme release, minute ventilation, patient activity score, cardiac output score, mixed venous oxygen score, cardiovascular pressure measures, and the like. However, the proper analysis of retrieved telemetered signals requires detailed medical subspecialty knowledge, particularly by cardiologists.
Alternatively, these telemetered signals can be remotely collected and analyzed using an automated patient care system. One such system is described in a related, commonly owned U.S. Pat. No. 6,312,378, issued Nov. 6, 2001, the disclosure of which is incorporated herein by reference. A medical device adapted to be implanted in an individual patient records telemetered signals that are then retrieved on a regular, periodic basis using an interrogator or similar interfacing device. The telemetered signals are downloaded via an internetwork onto a network server on a regular, e.g., daily, basis and stored as sets of collected measures in a database along with other patient care records. The information is then analyzed in an automated fashion and feedback, which includes a patient status indicator, is provided to the patient.
While such an automated system can serve as a valuable tool in providing remote patient care, an approach to systematically correlating and analyzing the raw collected telemetered signals, as well as manually collected physiological measures, through applied cardiovascular medical knowledge to accurately diagnose the onset of a particular medical condition, such as myocardial ischemia, is needed. One automated patient care system directed to a patient-specific monitoring function is described in U.S. Pat. No. 5,113,869 (""869) to Nappholz et al. The ""869 patent discloses an implantable, programmable electrocardiography (ECG) patient monitoring device that senses and analyzes ECG signals to detect ECG and physiological signal characteristics predictive of malignant cardiac arrhythmias. The monitoring device can communicate a warning signal to an external device when arrhythmias are predicted. Like the ECG morphology of malignant cardiac tachycardias, the electrocardiographic diagnosis of myocardial ischemia is well established and can be readily predicted using on-board signal detection techniques. However, the Nappholz device is limited to detecting tachycardias. The Nappholz device is patient specific and is unable to automatically take into consideration a broader patient or peer group history for reference to detect and consider the progression or improvement of myocardial ischemia. In addition, the Nappholz device does not take into account other physiological or chemical measures indicative of myocardial ischemia. Moreover, the Nappholz device has a limited capability to automatically self-reference multiple data points in time and cannot detect disease regression even in the individual patient. Also, the Nappholz device must be implanted and cannot function as an external monitor. Finally, the Nappholz device is incapable of tracking the cardiovascular and cardiopulmonary consequences of any rhythm disorder.
Consequently, there is a need for a systematic approach to detecting trends in regularly collected physiological and chemical data indicative of the onset, progression, regression, or status quo of myocardial ischemia diagnosed and monitored using an automated, remote patient care system. The physiological data could be telemetered signals data recorded either by an external or an implantable medical device or, alternatively, individual measures collected through manual means. Preferably, such an approach would be capable of diagnosing both myocardial ischemia conditions, as well as the symptoms of other diseases. In addition, findings from individual, peer group, and general population patient care records could be integrated into continuous, on-going monitoring and analysis.
The present invention provides a system and method for diagnosing and monitoring the onset, progression, regression, and status quo of myocardial ischemia using an automated collection and analysis patient care system. Measures of patient cardiovascular information are either recorded by an external or implantable medical device, such as an IPG, cardiovascular or heart failure monitor, or other therapeutic device, or manually through conventional patient-operable means. The measures are collected on a regular, periodic basis for storage in a database along with other patient care records. Derived measures are developed from the stored measures. Select stored and derived measures are analyzed and changes in patient condition are logged. The logged changes are compared to quantified indicator thresholds to detect the principal cardiovascular pathophysiological manifestations of myocardial ischemia: ST segment and/or T wave changes on the ECG, left ventricular wall motion changes, increased coronary sinus lactate production, increased serum creatinine kinase, increased serum troponin, increased ventricular arrhythmias, increased left ventricular end diastolic pressure, and reduced cardiac output.
An embodiment of the present invention is an automated system and method for diagnosing and monitoring myocardial ischemia and outcomes thereof. A plurality of monitoring sets is retrieved from a database. Each of the monitoring sets includes recorded measures relating to patient information recorded on a substantially continuous basis. A patient status change is determined by comparing at least one recorded measure from each of the monitoring sets to at least one other recorded measure. Both recorded measures relate to the same type of patient information. Each patient status change is tested against an indicator threshold corresponding to the same type of patient information as the recorded measures that were compared. The indicator threshold corresponds to a quantifiable physiological measure of a pathophysiology indicative of myocardial ischemia.
A further embodiment is an automated collection and analysis patient care system and method for diagnosing and monitoring myocardial ischemia and outcomes thereof. A plurality of monitoring sets is retrieved from a database. Each monitoring set includes recorded measures that each relate to patient information and include either medical device measures or derived measures calculable therefrom. The medical device measures are recorded on a substantially continuous basis. A set of indicator thresholds is defined. Each indicator threshold corresponds to a quantifiable physiological measure of a pathophysiology indicative of myocardial ischemia and relates to the same type of patient information as at least one of the recorded measures. A myocardial ischemia finding is diagnosed. A change in patient status is determined by comparing at least one recorded measure to at least one other recorded measure with both recorded measures relating to the same type of patient information. Each patient status change is compared to the indicator threshold corresponding to the same type of patient information as the recorded measures that were compared.
A further embodiment is an automated patient care system and method for diagnosing and monitoring myocardial ischemia and outcomes thereof. Recorded measures organized into a monitoring set for an individual patient are stored into a database. Each recorded measure is recorded on a substantially continuous basis and relates to at least one aspect of monitoring angina, reduced exercise capacity and/or respiratory distress. A plurality of the monitoring sets is periodically retrieved from the database. At least one measure related to myocardial ischemia onset, progression, regression, and status quo is evaluated. A patient status change is determined by comparing at least one recorded measure from each of the monitoring sets to at least one other recorded measure with both recorded measures relating to the same type of patient information. Each patient status change is tested against an indicator threshold corresponding to the same type of patient information as the recorded measures that were compared. The indicator threshold corresponds to a quantifiable physiological measure of a pathophysiology indicative of angina, reduced exercise capacity and/or respiratory distress.
The present invention provides a capability to detect and track subtle trends and incremental changes in recorded patient information for diagnosing and monitoring myocardial ischemia. When coupled with an enrollment in a remote patient monitoring service having the capability to remotely and continuously collect and analyze external or implantable medical device measures, myocardial ischemia detection, prevention, and tracking regression from therapeutic maneuvers become feasible.
Still other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein is described embodiments of the invention by way of illustrating the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the spirit and the scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.